Gary,
I would start by creating a cabinet that is the same size as the ladder. Use stretchers (with full dados) to create and position the rungs. Then take your end panels into the PE and set your angle snaps to whatever angle you need. Draw your stinger using the dados on the endpanel as guides. Use the create part using closed contour feature to cut out the perimeter of the stringers.
Gary,
FYI. Display boards will not nest at the control. You will want to use Display Panels.
And yes I think It would be easier to use cabinets, but that would be a user preference. I like using cabinets, because I can resize (to a certain point) and apply contraints.